1. Technical Field
The present invention relates to a transverse electric field mode liquid crystal display panel. Specifically, the present invention relates to a transverse electric mode liquid crystal display panel in which slits of an upper electrode extends along a signal line or a scanning line.
2. Related Art
The liquid crystal display panel has been used as a display unit in numerous electronic apparatuses since the liquid crystal display panel has features such as lightness, thinness, low power consumption in comparison to a CRT (Cathode Ray Tube). The liquid crystal display panel is a device which displays an image in such a manner that a direction of liquid crystal molecules aligned in a predetermined direction by performing a rubbing process on an alignment film is changed by an electric field and an amount of transmitted light or an amount of reflected light is varied.
As a method of applying the electric field to a liquid crystal layer of the liquid crystal display panel, there are a longitudinal electric field mode and a transverse electric field mode. The longitudinal electric field mode liquid crystal display panel mainly applies an electric field oriented in a vertical direction to liquid crystal molecules by a pair of electrodes disposed with the liquid crystal layer interposed therebetween. As the longitudinal electric field mode liquid crystal display panel, there are known a TN (Twisted Nematic) mode liquid crystal display panel, a VA (Vertical Alignment) mode liquid crystal display panel, a MVA (Multi-domain Vertical Alignment) mode liquid crystal display panel, and the like. In addition, the transverse electric field mode liquid crystal display panel mainly applies an electric field oriented in a horizontal direction to liquid crystal molecules by providing a pair of electrodes so as to be insulated from each other in the inside of one of a pair of substrates disposed with a liquid crystal layer interposed therebetween. As the transverse electric field mode liquid crystal display panel, there are known an IPS (In-Plane Switching) mode liquid crystal display panel in which a pair of electrodes do not overlap with other in plan view and a FFS (Fringe Field Switching) mode liquid crystal display panel in which a pair of electrodes overlap with each other in plan view. Since the transverse electric field mode liquid crystal display panel has an advantage of realizing a wide viewing angle, the transverse electric field mode liquid crystal display panel has widely been used in recent years.
In the transverse electric field mode liquid crystal display panel, slit-shaped openings extend so as to be slightly inclined in a rubbing direction and the liquid crystal molecules rotate in the same direction. In addition, in a color display liquid crystal display panel, it is possible to reduce a variation in colors in accordance with a viewing angle by realizing a multi-domain in which an inclination angle of the slit-shaped openings is divided into two positive and negative domains. However, an electric field cannot be generated in a desired direction in both ends of the slit-shaped openings. Therefore, when the slit-shaped openings extending in different directions are separated, an aperture ratio is reduced. Accordingly, the multi-domain having a high aperture ratio is realized by connecting the slit-shaped openings extending in the different directions to each other.
In the color display liquid crystal display panel, however, three sub-pixels of R (red), G (green), and B (blue) colors are normally formed in line and each one pixel is formed by a combination of the three sub-pixels. Since each one pixel normally has a substantial square, each one sub-pixel has a vertically long rectangle. Therefore, in the FFS mode liquid crystal display panel, since an electric field cannot be formed in the desired direction in both the ends of the slit-shaped openings provided in an upper electrode, a method of reducing a reduction in the aperture ratio by disposing the slit-shaped openings to extend in a vertical direction has been considered. When the slit-shaped openings extending in the different directions are connected to each other and the slit-shaped openings are disposed to extend in the vertical direction, the slit-shaped openings have a shape (or a chevron shape).
In the color display liquid crystal display panel, when the slit-shaped opening of the sub-pixel having the vertically long rectangle is formed in the shape, an area where no slit-shaped opening exits is broadened in upper and lower portions of the sub-pixel, thereby deteriorating the aperture ratio. In order to solve this problem, a liquid crystal display panel which has a zigzag shape formed by connecting a plurality of the slit-shaped openings having the shape to each other is disclosed in FIG. 68 of JP-A-2002-14374. In addition, a liquid crystal display panel which has the shape formed by matching a signal line to the slit-shaped opening, that is, the shape bent by matching the shape of the sub-pixel in a lengthwise direction to the slit-shaped opening is disclosed in FIG. 28 of JP-A-2008-70838.
In recent years, there has been devised a FFS mode liquid crystal display panel in which a lower electrode operates as a pixel electrode and an upper electrode operates as a common electrode by forming an inter-electrode insulating film on the lower electrode and forming the upper electrode having slit-shaped openings on the surface of the inter-electrode insulating film across all the sub-pixels. Since the FFS mode liquid crystal display panel having this configuration has an advantage of considerably improving brightness and contrast, the FFS mode liquid crystal display panel has been applied to a device which includes a slit-shaped opening having the shape.
However, in this liquid crystal display panel, a way of disposing the slit-shaped opening when the slit-shaped opening having the shape extending in the same direction as that of a signal line in a light-shielding film (black matrix) of a color filter substrate is formed in the upper electrode formed across the signal lines is not taken into consideration. On the other hand, in a liquid crystal display panel in which the upper electrode having the slit-shaped opening is not formed across the signal line and the upper electrode operates as a pixel electrode, the width of the light-shielding film is equal to or larger than that of the signal line. When a color filter substrate which includes the light-shielding film having this configuration is applied to a liquid crystal display panel in which the upper electrode operates as a common electrode, and particularly, when the slit-shaped opening is formed close to the signal line in order to make the aperture ratio larger, a problem occurs in that a brightly displayed region of the circumference of the slit-shaped opening is shielded from light by the light-shielding film and thus brightness deteriorates.